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The first 50Myr of dinosaur evolution: macroevolutionary pattern and morphological disparity
Stephen L Brusatte1, Michael J Benton, Marcello Ruta
1Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK. sbrusatte@amnh.org
Biology Letters
|September 25, 2008
Summary
Dinosaur evolution reveals complexity beyond simple ecological release. While dinosaur diversity increased steadily, their morphological disparity peaked in the Triassic, not the Jurassic, challenging previous theories.
Area of Science:
- Paleontology
- Macroevolutionary Biology
- Earth History
Background:
- The Late Triassic and Early Jurassic evolutionary radiation of dinosaurs is a critical event in Earth's history.
- Previous studies lacked detailed analysis of macroevolutionary components like origination, diversity, abundance, and disparity.
- Understanding dinosaur radiation requires disentangling these distinct evolutionary processes.
Purpose of the Study:
- To calculate the morphological disparity and taxonomic diversity of dinosaurs during the Late Triassic and Early Jurassic.
- To investigate the driving mechanisms behind dinosaur evolutionary radiation.
- To test the hypothesis of ecological release-driven morphospace expansion in the Early Jurassic.
Main Methods:
- Calculation of morphological disparity (morphospace occupation) for dinosaurs.
- Development of new measures for taxonomic diversity.
- Analysis of dinosaur and Crurotarsan archosaur evolutionary patterns across the Triassic-Jurassic boundary.
Main Results:
- Crurotarsan archosaurs were more morphologically disparate than dinosaurs in the Triassic but suffered a major extinction at the Triassic-Jurassic boundary.
- Dinosaur morphological disparity showed only a slight, non-significant increase post-extinction, contradicting ecological release hypotheses.
- The primary increase in dinosaur disparity occurred during the Carnian to Norian stages of the Triassic.
- Dinosaur diversity steadily increased throughout the period, with significant diversification and abundance in the Early Jurassic.
Conclusions:
- Dinosaur evolutionary radiation involved decoupled components of diversity, disparity, and abundance.
- The major expansion of dinosaur morphological disparity occurred within the Triassic, not primarily in the Early Jurassic.
- The macroevolutionary pattern of early dinosaur evolution (first 50 million years) is more intricate than previously assumed, with distinct drivers for diversity and disparity.
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